Recently, personal computers and communication appliances are much more advanced in speed, and electronic components used therein are required to be reduced in size and have sufficient measures against higher frequencies. Accordingly, a capacitor, one of such electronic components, is demanded to be larger in capacity and lower in impedance. In particular, a CPU driving power supply circuit of a computer is required to have a sufficient absorbing performance of noise and ripple current as a high frequency countermeasure in circuit design. There is hence a stronger demand for an electrolytic capacitor of low ESR (equivalent series resistance), low ESL (equivalent series inductance), high ripple current resistance and large capacity. To meet such demand, at the present, a multiplicity of small chip capacitors are disposed around the CPU at close positions to the CPU.
FIG. 53 shows a peripheral area of a CPU in a conventional configuration. Connection pins (hereinafter called pins) 402 are provided at the lower side of an IC 401 represented by a CPU. An IC socket (hereinafter called socket) 403 is soldered to a printed circuit board (hereinafter called board) 404. Chip capacitors (hereinafter called capacitors) 405 are mounted closely to the IC 401 composed in this manner. A similar mounting arrangement, using resistors instead of the capacitors in the configuration described above, is disclosed, for example, in Japanese Unexamined Patent Publication No. S60-130150.
The IC 401 has 478 of pins 402, and a distributing wiring pattern (not shown) from the IC 401 is provided on the board 404 mounting the socket 403. In such mounting manner, as the number of components to be mounted increases, the mounting positions of the capacitors 405 around the IC 401 and other electronic components not shown in the drawing are moved away from the IC 401, and there becomes a sortage of mounting area.
On the other hand, the operating frequency of the CPU continues to go up, and in order to absorb noise and supply current, chip capacitors of large capacity, low ESR and low ESL must be disposed as close to the CPU as possible. It is now hard to meet such demand by the present technology.
Specifically, the height of the socket 403 is about 3 mm, and the distance from the socket 403 to the capacitors 405 is about tens of millimeters, and the ESL becomes higher relative to the CPU, and the impedance rises as the frequency becomes higher. As a result, the performance of the capacitors of low ESL cannot be exhibited sufficiently in a high frequency.